Known autoclaves which are presently used for the manufacture of fiber compound parts comprise a hot air source within the pressure container receiving the objects to be treated as the only heat source. A stream of hot air from the hot air source is directed through the pressure chamber to heat up its interior including the objects to be treated which are arranged therein. Often, air flow guiding sheets and air circulating ventilators are provided in the pressure chamber delimited by the pressure container for guiding this air stream. Heating the objects arranged in the pressure chamber by hot air is not without disadvantages. This heating only takes place via the surfaces of the objects over which the hot air flows and from which the heat energy has to get into the volume of the objects by means of heat conduction. Even the surfaces of the objects are not uniformly heated up by the hot air because, for example, of shadowing effects and other non-uniformities in the arrangement of the surfaces with regard to the hot air flow. Core areas of the objects having different distances to the surfaces of the objects are heated up with different rates, even if the surfaces of the objects are uniformly heated up. Further, the general efficiency in heat transfer onto the surfaces via convection is only low with the usual laminar air flows, as the flow velocity of the hot air goes down to zero in a boundary layer at the surfaces over which the air flows so that these boundary layers provide an unwanted thermal isolation layer about the respective object to be heated up. In addition, the hot air in the pressure chamber of the autoclave not only heats up the objects to be treated but also the autoclave itself. Even if the autoclave has a good internal isolation, much more than one half of the total heating power in a known hot air autoclave is not used for heating up the objects to be treated but for heating up the pressure container and the further contents of the pressure container like, for example, moulds for the object to be treated and their surrounding atmosphere.
A method and a microwave system for thermal processing shaped bodies of starting materials into three-dimensional composites of stable shape are known from DE 199 29 666 C2. Here, microwave radiation is coupled out of at least one microwave source via an associated coupling means into a processing chamber and directed onto an associated wave-optical mirror which reflects the microwave radiation into the processing volume and rearranges the amplitude distribution of the microwave radiation in such a way that a plane wave front is formed in the processing volume to provide for homogenous or at least sufficiently homogeneous field conditions. In this way, the thermal treatment of starting materials for the manufacture of fiber compound parts by means of microwave radiation shall be enabled in that inhomogenities of the temperature distribution over large size objects during their thermal treatment using microwave radiation are avoided. The method known from DE 199 29 666 C2 and the microwave system also described there are not yet applied in practice. One obstacle for the practical application is that suitable wave-optical mirrors are not available. Further, processing very large objects according to the known method using the known microwave system would require the application of very high power microwave sources. Further, even with ideally homogenous field conditions of the applied microwave radiation, a homogenous temperature distribution over the objects to be treated could not be ensured because of different absorptions, reflections and shadowing of the microwave radiation within the processing volume already by the objects to be treated. A simultaneous pressure treatment in addition to the temperature treatment is not provided by the method known form DE 199 29 666 C2 and the microwave system described therein.
An autoclave for pressure and temperature treatment of objects using microwave radiation as a heat source is known from WO 03/053105. Here, the pressure chamber is designed as a cavity resonator for the microwaves coupled-in from the outside of the pressure container. Thus, the diameter of the pressure chamber has to be exactly tuned to the frequency of the microwaves coupled-in. It may not have any desired value. The microwaves are coupled into the pressure chamber through the pressure resistant wall of the pressure container via two or three rows of microwave antennas which rows are evenly distributed in circumferential direction. Although it is generally intended to provide a plurality of microwave sources in bigger systems to limit the microwave power per microwave antenna, their actual number remains small, as they are to be also evenly distributed in axial direction. Further, the arrangement of the microwave sources also has to be adapted to the end of forming a single stationary wave in the pressure chamber. To form each individual microwave antenna, a body of dielectric material having a square cross section extends through the pressure resistant wall. Outside of the pressure container, a hollow wave guide having a square free cross section is attached to each of these microwave antennas. This construction has no stability in the range of higher pressures, as it is difficult to anchor the bodies of dielectric material in the pressure resistant wall in a pressure tight and pressure resistant way. Further, it does not seem to be realistic that a stationary microwave having nodes at the pressure resistant wall can be formed in the pressure chamber independently of the objects loaded into the pressure container having a fixed diameter. It does also not seem to be realistic that, upon constructing the pressure chamber as a cavity resonator for the microwave, a homogenous distribution of the microwave intensity over the pressure chamber is actually achieved.
Thus, a need remains for an autoclave for pressure and temperature treatment of objects, particularly in the manufacture of fibre compound parts, which allows for homogeneously heating up large scale objects arranged in the pressure chamber of the autoclave at a low input of energy.